Suction cup



FIG. 1 is a perspective view of my design for a suction cup;

FIG. 2 is a front view thereof;

FIG. 3 is a back view thereof;

FIG. 4 is a left side view of my suction cup, the right side being a mirror image thereof; and,

FIG. 5 is a top view of my suction cup, the bottom view being a mirror image thereof. 

The ornamental design for a suction cup, as shown and described. 